tcg: Create struct CPUTLB

tcg: Create struct CPUTLB

Move all softmmu tlb data into this structure.  Arrange the
members so that we are able to place mask+table together and
at a smaller absolute offset from ENV.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>